Skunks are common in rural areas, but they are increasingly seen in population centers, as well. They are skilled diggers, but they are generally more interested in eggs (and occasionally chicken feed) than chickens. They typically carry the egg away intact. However, they may attack chicks, and in rare cases may maul older chickens, usually preferring bantams and other small breeds.
A skunk that carries away eggs will leave no trace other than the absence of eggs. If it takes a chick, it will usually enter the abdomen. In the rare event that a skunk attacks older chickens, it will maul them badly, generally biting the head and neck and leaving feathers scattered everywhere. How much of a full-grown chicken a skunk will eat varies. Of course, a lingering odor is a dead giveaway that a skunk was the predator in question.
Electric poultry netting is quite sufficient to deter skunks from the eggs and laying hens. Chicks should be kept in a secure brooder. A stock tank in a garage is often a safe place to brood chicks, but if you raise enough that they must be kept in a separate brooder building, consider extra measures to secure your chicks. Options include placing paving slabs around the exterior, burying several inches of hardware cloth next to the outside walls, or posting a guard dog on duty nearby.
Weasels can be devastating to a small flock. These wily nocturnal predators may travel in packs and slip through tiny gaps and openings. They eat very little of their prey, often killing for the fun of it. They also eat eggs.
If you find multiple chickens lying around dead for no apparent reason, take a closer look. Weasels usually bite heads and necks, sometimes the chest. A weasel may also take the intestines out of the body cavity through the back end. You might see feathers bitten into small, irregular pieces. Another oddity you may discover is dead chickens neatly stacked up. Finally, a weasel leaves behind a faint scent similar to that of a skunk.
Weasels can be very difficult to keep out of coops. Sturdy welded wire with openings no larger than 1/2″ is a good option. Use it to line any and all gaps and crevices. You can also bury it around the outside of a stationary coop or brooder building to prevent digging. Be sure to keep the coop in good repair, patching holes as necessary. Because weasels are prey to hawks, owls, coyotes, and other larger predators, siting your chickens in an open, mowed field with no cover to hide under can also prevent weasel attacks.